Microfluidic device having microchips

ABSTRACT

After a second plate member  3  is inserted into a space which is surrounded by side walls  6   a  through  6   d  of a first plate member  2 , the bonded surface  3   a  of the second plate member  3  is bonded and fixed to the bonded surface  2   a  of the first plate member  2  by an adhesive to form a sample handling unit  1 . At this time, the second plate member  3  is positioned by protrusions  35  and  36  of the first plate member  2  in X and Y directions, and positioned and fixed by holding members  8  through  13  and inside holding members  26  and  27  in Z directions (normal directions on an external surface  7 ). A microfluidic device  101  includes microchips  106  through  108  of plural kinds having passages  132  through  134  for transporting a sample, and a base member  102  on which the microchips  106  through  108  are arranged. After the base member  102  and the microchips  106  through  108  are separately formed, microchips  106  through  108  of kinds necessary for intended purpose, such as analysis of the sample, are selected to be suitably combined to be positioned and fixed on the base member  102  to form the microfluidic device  101 . By causing the positioning holes  127  of the microchips  106  through  108  to engage the positioning protrusions  128  of the base member  102 , the microchips  106  through  108  are positioned with respect to the base member  102.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. Ser. No. 10/832,848filed Apr. 27, 2004, now U.S. Pat. No. 7,422,725.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a sample handling unitapplicable to a microchip, and a microfluidic device having a pluralityof microchips. More specifically, the invention relations to a samplehandling unit capable of being widely applied to a microchip (e.g., amicrochip of a type for moving a very small amount of sample (specimen)in a microchannel, or a microchip of a type for housing and holding avery small amount of sample (specimen) in a microwell) or the like in atechnical field called integrated chemistry, and the invention alsorelates to a microfluidic device which is used for carrying out theseparation, analysis or the like of a very small amount of sample in afluid, or for carrying out the mixing, reaction, concentration or thelike of a very small amount of sample.

2. Description of the Prior Art

In recent years, there is known a technique called integrated chemistryfor forming a fine groove (recessed portion) having a width and depth ofabout tens to two hundreds micrometers in a microchip (sample handlingunit) of a glass or plastic, to use the fine groove as a liquid passage,reaction vessel or separation/purification detecting vessel, tointegrate a complicated chemical system into the microchip. According tosuch integrated chemistry, a microchip (Lab-on-a-chip) having a finegroove used in various tests is called μ-TAS (Total Analytical System)if the use of the microchip is limited to analytical chemistry, and themicrochip is called microreactor if the use of the microchip is limitedto a reaction. When various tests, such as analyses, are carried out,integrated chemistry has advantages that the time to transport diffusemolecules is short due to small space and that the heat capacity of aliquid phase is very small. Therefore, integrated chemistry is noticedin the technical field wherein a micro space is intended to be utilizedfor carrying out analysis and chemical synthesis. Furthermore, the term“test” means to carry out any one or combination of operations andmeans, such as analysis, measurement, synthesis, decomposition, mixing,molecular transportation, solvent extraction, solid phase extraction,phase separation, phase combination, molecule acquisition, culture,heating and cooling.

In such integrated chemistry, a capillary electrophoresis chip used in atest in the field of, e.g., biochemistry, is a chip of a glass orplastic which has a fine groove or circular recessed portion having awidth and depth of about 10 to 200 micrometers to use the fine groove orrecessed portion as a liquid passage or reaction vessel to separate andidentify a very small amount of vital material, such as a nucleic acidor protein, or another low molecular material, so that the material tobe treated therein has a very small volume of nanoliters to picoliters.Therefore, it is required to precisely form the fine groove.

As methods for forming a fine groove (a hollow portion) in a glass orplastic, there are blow molding and lost-core methods. By these methods,it is difficult to precisely form a fine groove having a cross sectiontens micrometers square. Therefore, there is often adopted a method forforming a fine groove in a surface of a first plate member (a firstmember) of a glass, plastic or silicon to bond a second plate member (asecond member), which is formed of the same material as that of thefirst plate member so as to have the same size as that of the firstplate member, to the surface of the first plate member having the finegroove by adhesion or welding to form a microchip as a sample handlingunit (see Japanese Patent Laid-Open Nos. 2000-246092 and 2000-288381).

However, if the sample handing device, which is formed by bonding thefirst plate member to the second plate member by adhesion or welding,slides down and drops from an experimenter's hand onto the floor or thelike when various tests are carried out, the shock of the collision withthe floor or the like causes external force, such as shearing force, toact on the bonded surface of the first plate member to the second platemember, so that there is the possibility that the bonded surface may bepartially broken (cracked) to damage sealing performance around amicrochannel to damage the function of the microchannel and/or to peelthe first plate member off from the second plate member.

In recent years, there have been prosperously studied devices capable ofcarrying out separation, analysis, mixing, reaction, concentration orthe like of a sample in a fine space called Lab-on-a-chip, μ-TAS,microreactor or the like. In such devices, there are many advantages inthat the amount of a sample to be analyzed can be decreased, the size ofsystem can be decreased, the time to carry out analysis or the like canbe shortened, and so forth.

For example, there are known microfluidic devices for electrophoresiswherein a fine passage (microchannel) is formed in a fine space forseparating and analyzing vital molecules, such as DNA and proteins,which serve as samples (specimens) and microfluidic devices for POC(Point-of-Care) wherein a reservoir or fine passage is formed for mixinga collected blood with a plurality of predetermined solutions to observea catalytic reaction. Usually, these microfluidic devices have a singlemicrofluidic system.

On the other hand, there are known microfluidic devices having aplurality of microfluidic systems (see WO99/15876, WO99/15888, and US2003/0006141A1).

However, in these conventional devices, a large number of microchannelscomprising fine grooves must be formed in a chip so as to be set inarray. If such a chip having a large number of microchannels is intendedto be formed by injection molding, it is difficult to work a die.Therefore, the cost of producing the die is very high, and the price ofthe chip is very high. Even if such a chip is formed by a working methodother than injection molding, e.g., a working method utilizing asemiconductor working technique, such as photolithography, when a largenumber of microchannels comprising fine grooves are simultaneouslyformed in a chip (plate), the yields deteriorate to inhibit the price ofthe chip from decreasing.

In addition, in the above described conventional devices, a large numberof microchannels are formed directly in a chip. Therefore, it is notpossible to change the structure of the chip in accordance with intendedpurpose or the like, so that there is a problem in that the expensivechip can be only used for a specific intended purpose.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to eliminate theaforementioned problems and to provide a sample handling unit which isformed by bonding a plurality of members and which is capable ofeffectively preventing a bonded surface from being partially broken andpreventing bonded members from being peeled off from each other even ifshocks are given to the unit.

It is another object of the present invention to eliminate theaforementioned problems and to provide a microfluidic device capable ofchanging the structure of a chip in accordance with intended purpose orthe like.

In order to accomplish the aforementioned and other objects, accordingto one aspect of the present invention, there is provided a samplehandling unit for handling a sample, the unit comprising: a first memberhaving a surface; and a second member having a surface which is bondedto the surface of the first member to define a space between the firstand second members for handling a sample, the second member having aside face which extends from an edge of the surface of the secondmember, wherein the first member has a protruding wall which protrudesfrom the surface of the first member so as to face the side face of thesecond member.

Furthermore, throughout the specification, the term “sample” means amaterial used in various operations and means, such as such as analysis,measurement, synthesis, decomposition, mixing, molecular transportation,solvent extraction, solid phase extraction, phase separation, phasecombination, molecule acquisition, culture, heating and cooling. Forexample, in an operation, such as analysis or measurement, the term“sample” means a specimen to be operated, and in a synthesis operation,the term “sample” means a raw material before synthesis or a compound orthe like after synthesis.

In the above described sample handling unit, the space may be a spacefor allowing the sample to move therein, or a space for housing thereinthe sample. In addition, a second space may be defined between the firstand second members, the space being a space for allowing the sample tomove therein, and the second space being a space for housing therein thesample. The protruding wall is preferably positioned so as to face acorner of the second member. The protruding wall preferably protrudesfrom a plane including an opposite surface of the second member which isopposite to the surface of the second member. The protruding wall mayhave a protrusion which contacts the side face of the second member forpositioning the second member with respect to the first member. Thefirst member may have a holding member for biasing the second membertoward the first member to hold the second member on the first member,or a pair of holding members for biasing the second member toward thefirst member to hold the second member on the first member. The holdingmember may have an engaging portion for engaging an opposite surface ofthe second member which is opposite to the surface of the second member.The second member may have an inclined surface in a portion facing theholding member, the inclined surface being inclined with respect to thesurface of the second member, and the holding member may have anengaging portion for engaging the inclined surface of the second memberto bias the second member toward the first member. One of the first andsecond members may have a hole, and the other of the first and secondmembers may have a pair of inside holding members for engaging the holeto hold the second member on the first member. In this case, one of thepair of inside holding members may engage a first portion of the hole soas to bias the one of the first and second members in a first direction,and the other of the pair of inside holding members may engage a secondportion of the hole, which is opposite to the first portion thereof, soas to bias the one of the first and second members in a second directionopposite to the first direction, the pair of inside holding membersbeing associated with each other for holding the second member on thefirst member. In addition, the hole may have an engaged portion whichprotrudes toward the pair of inside holding members, and each of thepair of inside holding members may have an engaging portion whichprotrudes toward the hole, the engaging portion of each of the pair ofinside holding members engaging the engaged portion of the hole so as topress the second member on the first member. The hole and the insideholding members may be arranged in the vicinity of the space definedbetween the first and second members. The inside holding members may beformed so as not to protrude from a plane including an opposite surfaceof the one of the first and second members, the opposite surface beingopposite to the surface of the one of the first and second members. Theholding member may have a protrusion which contacts the side face of thesecond member for positioning the second member with respect to thefirst member.

According to another aspect of the present invention, there is provideda sample handling unit for handling a sample, the unit comprising: afirst member having a surface; and a second member having a surfacewhich is bonded to the surface of the first member to define a spacebetween the first and second members for handling a sample therein, thesecond member having a side face which extends from an edge of thesurface of the second member, wherein the surface of the first member islarger than the surface of the second member so that the first memberprotrudes from the edge of the surface of the second member.

In this sample handling unit, the space may be a space for allowing thesample to move therein, or a space for housing therein the sample. Inaddition, a second space may be defined between the first and secondmembers, the space being a space for allowing the sample to movetherein, and the second space being a space for housing therein thesample. One of the first and second members may have a hole, and theother of the first and second members may have a pair of inside holdingmembers for engaging the hole to hold the second member on the firstmember. In this case, one of the pair of inside holding members mayengage a first portion of the hole so as to bias the one of the firstand second members in a first direction, and the other of the pair ofinside holding members may engage a second portion of the hole, which isopposite to the first portion thereof, so as to bias the one of thefirst and second members in a second direction opposite to the firstdirection, the pair of inside holding members being associated with eachother for holding the second member on the first member. In addition,the hole may have an engaged portion which protrudes toward the pair ofinside holding members, and each of the pair of inside holding membersmay have an engaging portion which protrudes toward the hole, theengaging portion of each of the pair of inside holding members engagingthe engaged portion of the hole so as to press the second member on thefirst member.

According to a further aspect of the present invention, a microfluidicdevice comprises: a base member; and a plurality of microchips, each ofwhich has a space defined therein for transporting a sample, theplurality of microchips being mounted on the base member so as to be setin array.

In this microfluidic device, each of the plurality of microchips mayhave a recessed portion which is closed by the base member to define thespace. The plurality of microchips may be detachably mounted on the basemember. The base member may have a chip pressing claw, and the pluralityof microchips may be detachably held by the chip pressing claw of thebase member. The space may be a passage for allowing the sample to movetherein. The passage may have a storage portion for storing therein thesample. The storage portion of one of the plurality of microchips may becommunicated with the storage portion of another of the plurality ofmicrochips via a communication passage formed in the base member. One ofadjacent two of the plurality of microchips may have an engagingprotrusion which protrudes toward the other of the adjacent two of theplurality of microchips, and the other of the adjacent two of theplurality of microchips may have an engaged recess which is engaged withthe engaging protrusion of the one of adjacent two of the plurality ofmicrochips. The plurality of microchips may be positioned with respectto the base member by positioning means.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood more fully from the detaileddescription given herebelow and from the accompanying drawings of thepreferred embodiments of the invention. However, the drawings are notintended to imply limitation of the invention to a specific embodiment,but are for explanation and understanding only.

In the drawings:

FIG. 1 is a plan view of a preferred embodiment of a sample handing unitaccording to the present invention;

FIG. 2 is a sectional view of the sample handling unit taken along lineII-II of FIG. 1;

FIG. 3 is a plan view of a first plate member forming the samplehandling unit of FIG. 1;

FIG. 4 is a sectional view of the first plate member taken along lineIV-IV of FIG. 3;

FIG. 5 is a plan view of a second plate member forming the samplehandling unit of FIG. 1;

FIG. 6 is a sectional view of the second plate member taken along lineVI-VI of FIG. 5;

FIG. 7 is a plan view of a first plate member of another preferredembodiment of a sample handling unit according to the present invention;

FIG. 8 is a plan view of a second plate member of another preferredembodiment of a sample handling unit according to the present invention;

FIG. 9 is a sectional view of a part of a sample handling unit whereinthe first plate member of FIG. 7 is bonded to the second plate member ofFIG. 8;

FIG. 10 is an enlarged sectional view of a part of a modified example ofa sample handling unit in the preferred embodiment, which showsengagement of a holding member;

FIG. 11 is a plan view of another modified example of a sample handlingunit in the preferred embodiment;

FIG. 12 is a plan view of another modified example of a sample handlingunit in the preferred embodiment;

FIG. 13A is a plan view of another modified example of a sample handlingunit in the preferred embodiment, and FIG. 13B is a side view of a partof the sample handling unit of FIG. 13A;

FIG. 14 is a plan view of another modified example of a sample handlingunit in the preferred embodiment;

FIG. 15 is a plan view of another modified example of a sample handlingunit in the preferred embodiment;

FIG. 16 is a sectional view of another modified example of a samplehandling unit in the preferred embodiment, which corresponds to FIG. 2;

FIG. 17A is a plan view of the first preferred embodiment of amicrofluidic device according to the present invention, and FIG. 17B isa partially sectional side view of the microfluidic device taken alongline XVIIB-XVIIB of FIG. 17A;

FIG. 18A through 18C are plan views of microchips in the first preferredembodiment of the present invention, wherein FIG. 18A shows a microchipof the first kind, FIG. 18B shows a microchip of the second kind, andFIG. 18C shows a microchip of the third kind;

FIG. 19A is a plan view of the second preferred embodiment of amicrofluidic device according to the present invention, and FIG. 19B isa partially sectional side view of the microfluidic device taken alongline XIXB-XIXB of FIG. 19A;

FIG. 20 is an enlarged view of a part of FIG. 19A;

FIG. 21 is an enlarged sectional view of a part of FIG. 19B;

FIG. 22 is a plan view of a part of the third preferred embodiment of amicrofluidic device according to the present invention;

FIG. 23 is a plan view of a part of the fourth preferred embodiment of amicrofluidic device according to the present invention;

FIG. 24 is a plan view of a part of the fifth preferred embodiment of amicrofluidic device according to the present invention; and

FIG. 25 is an exploded perspective view of the sixth preferredembodiment of a microfluidic device according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the accompanying drawings, particularly to FIGS. 1through 16, the preferred embodiments of a sample handling unitaccording to the present invention will be described below in detail. Ineach of the following preferred embodiments, a sample handling unit of aplastic used as a capillary electrophoresis chip will be described as anexample.

FIGS. 1 through 6 show a preferred embodiment of a sample handling unit1 according to the present invention. FIG. 1 is a plan view of thesample handling unit 1, and FIG. 2 is a sectional view of the samplehandling unit 1 taken along line II-II of FIG. 1. FIG. 3 is a plan viewof a first plate member (first member) 2 forming the sample handlingunit 1 of FIG. 1, and FIG. 4 is a sectional view of the first platemember 2 taken along line IV-IV of FIG. 3. FIG. 5 is a plan view of asecond plate member (second member) 3 forming the sample handling unit 1of FIG. 1, and FIG. 6 is a sectional view of the second plate member 3taken along line VI-VI of FIG. 5.

The sample handling unit 1 shown in these figures comprises the firstplate member 2 and the second plate member 3 bonded and fixed thereto.The first and second plate members 2 and 3 forming the sample handlingunit 1 are formed of, e.g., polycarbonate (PC), polymethylmethacrylate(PMMA), ultraviolet curable resin or the like, and are preferably formedof the same material. If the first plate member 2 and the second platemember 3 are thus formed of the same material, the surface charge of thefirst plate member 2 can be equal to that of the second plate member 3,so that the electroosmosis flow to a sample during electrophoresis canbe uniform to cause the flow of the sample to be constant. In addition,if the first plate member 2 and the second plate member 3 are formed ofthe same material, when an adhesive is allowed to permeate a gap betweenthe bonded surfaces 2 a and 3 a of the first and second plate members 2and 3 due to capillarity, the behavior of the adhesive toward the firstplate member 2 is the same as that toward the second plate member 3, sothat the movement of the adhesive due to capillarity is smooth.Furthermore, the first plate member 2 is larger than the second platemember 3 so as to protrude from the side faces of the second platemember 3 by a predetermined width (e.g., by side walls 6 a through 6 das described later).

The first plate member 2 has a substantially rectangular planar shape.The first plate member 2 has a first elongated linear fine groove(recessed portion) 4 in the substantially central portion of its topface (the bonded surface 2 a serving as a first surface), and a secondfine groove (recessed portion) 5 substantially perpendicular to thefirst fine groove 4. The first and second fine grooves 4 and 5 have asubstantially square cross section (the length of one side is in therange of from 50 to 100 micrometers), and an overall length of a fewcentimeters. Around the fine grooves 4 and 5 of the first plate member2, the bonded surface 2 a is formed. From the edges of the first platemember 2, side walls 6 a through 6 d protrude for housing the secondplate member 3 in a space surrounded by the side walls 6 a through 6 b.

The side walls 6 a through 6 d of the first plate member 2 have such aheight that the side walls 6 a through 6 d protrude from the externalsurface 7 of the second plate member 3 when the second plate member 3 isbonded and fixed to the first plate member 2. The side walls 6 a through6 d of the first plate member 2 are partially cut out. In the cut-outportions of the side walls 6 a through 6 d, elastically deformableholding members 8 through 13 are integrally formed independently of theside walls 6 a through 6 d. The holding members 8, 9, 11 and 12 arearranged on the sides of both end portions of the side walls 6 a and 6 cfacing longitudinal side faces 14 and 15 of the second plate member 3.The holding members 8 and 9 on the side of one side wall 6 a of thefirst plate member 2 face the holding members 12 and 11 on the side ofthe other side wall 6 c of the first plate member 2. The holding members10 and 13 are arranged so as to face the central portions of the sidefaces 16 and 17 substantially perpendicular to the side faces 14 and 15of the second plate member 3.

As shown in FIG. 2, the holding members 8 through 13 have an elasticallydeformable support portion 18 vertically extending upwards from thefirst plate member 2, and a hook portion 21 inwardly protruding from thetip end portion of the support portion 18 to be engageable with theexternal surface (outside engaging portion 20) of the second platemember 3. The hook portion 21 has an inclined surface 23 for contactingand guiding a chamfered portion 22, which is formed on the edge of theside face of the second plate member 3, when the second plate member 3is mounted on the first plate member 2 from top. The bottom face 24 ofthe hook portion 21 is designed to contact the outside engaging portion20 of the second plate member 3 to press the second plate member 3 onthe first plate member 2 so as to prevent the second plate member 3 frommoving in a direction (upwards in FIG. 2) in which the second platemember 3 is peeled off from the first plate member 2. In such holdingmembers 8 through 13, the inclined surface 23 of the hook portion 21 ispushed by the chamfered portion 22 of the second plate member 3 when thesecond plate member 3 is mounted on the first plate member 2 from top inFIG. 2, so that the support portion 18 is deformed by external forceacting on the inclined surface 23 to allow the second plate member 3 tomove toward the first plate member 2. Then, when the second plate member3 is pushed into a predetermined portion on the first plate member, thesupport member 18 is designed to restore to the original attitude by itselasticity, so that the hook portion 21 engages the outside engagingportion 20 of the second plate member 3. Furthermore, if the top of eachof the holding members 8 through 13 is designed so as not to protrudefrom the external surface 7 of the second plate member 3 and if the topof each of the side walls 6 a through 6 d is designed so as not toprotrude from the external surface 7 of the second plate member 3, whena spotting device or the like moves along the external surface 7 of thesecond plate member 3, the movement of the spotting device or the likeis not obstructed by the top of each of the side walls 6 a through 6 dand holding members 8 through 13, so that the ability of operation, suchas spotting operation, is improved.

On the side of the bonded surface 2 a of the first plate member 2, thereare formed a plurality of inside holding members 26 and 27 which arehooked on the inside engaging portions 25 of the second plate member 3.The inside holding members 26 and 27 are arranged in the vicinity of thefirst fine groove 4 on both sides thereof so as to be symmetrical withrespect to the first fine groove 4. That is, the bonded surface 2 a onone side of the first fine groove 4 and the bonded surface 2 a on theother side thereof are formed with the pair of inside holding members 26and 27, respectively, which are arranged back to back and which aredisplaced from each other so as not to interfere with each other. Eachof the inside holding members 26 and 27 substantially has the same shapeas that of each of the above described holding members 8 through 13.Each of the inside holding members 26 and 27 has an elasticallydeformable support portion 28 protruding from the first plate member 2,and a hook portion 30 which is formed so as to protrude from the tip endportion of the support portion 28 to the side and which is hooked on theinside engaging portion 25 of the second plate member 3. The upperportion of the hook portion 30 is formed with an inclined surface 33 forcontacting and guiding a chamfered portion 32, which is formed on thebottom end of a hole 31 of the second plate member 3, when the secondplate member 3 is mounted on the first plate member 2 from top in FIG.2.

If the inclined surface 33 of the hook portion 30 is pushed by thechamfered portion 32 of the second plate member 3, the support portion28 is flexibly deformed to allow the inside holding members 26 and 27 topass through the hole 31. Then, if the hook portion 30 passes throughthe hole 31 to mount the second plate member 3 on the first plate member2 at a predetermined position, the support portion 28 restores to theoriginal attitude, so that the hook portion 30 engages the insideengaging portion 25 of the second plate member 3. Then, the bottomsurface 34 of the hook portion 30 presses the inside engaging portion 25on the bonded surface 2 a of the first plate member 2. As a result, thesecond plate member 3 is fixed at a position near the first fine groove4 of the first plate member by means of the inside holding members 26and 27. Furthermore, as shown in FIG. 2, the hook portion 30 is designedto push the bottom face of the inside engaging portion 25, which is arecessed portion formed in the upper open end of the hole 31. The insideholding members 26 and 27 are formed so that the top ends 26 a and 27 athereof do not protrude from the external surface 7 of the second platemember 3.

On the surfaces (inside surfaces) of the side walls 6 a through 6 d ofthe first plate member 2 facing the side faces 14 through 17 of thesecond plate member 3, there are formed substantially semi-sphericalprotrusions 35 serving as positioning means for preventing the secondplate member 3 from being displaced from the first plate member 2 (in Xand Y directions in FIGS. 1 and 2). The protrusions 35 are arranged inthe substantially central portion in longitudinal directions of thesecond plate member 3 substantially having the rectangular planar shape,and arranged in both end portions in lateral directions of the secondplate member 3. Protrusions 36 similar to the protrusions 35 are formedon surfaces of the holding members 8 through 13 facing the second platemember 3. Thus, each of the four side faces 14 through 17 of the secondplate member 3 is positioned so as to be well-balanced by the threeprotrusions 35 and 36 with respect to the first plate member 2. In theholding members 8 through 13, the protrusion 36 on the surface of thesupport portion 18 facing the second plate member 3 is designed to bepressed on the side faces 14 through 17 of the second plate member 3 byelectrically deformation force of the support portion 18.

The second plate member 3 is a thin plate member which is housed in aspace surrounded by the side walls 6 a through 6 d of the first platemember 2, and has a substantially rectangular planar shape. In thesecond plate member 3, through holes 37 for communicating both endportions of the first fine groove 4 of the first plate member 2 and bothend portions of the second fine groove 5 thereof with outsideenvironment are formed so as to face both end portions of the first finegroove 4 of the first plate member 2 and both end portions of the secondfine groove 5 thereof.

The second plate member 3 has outside engaging portions 20 which arearranged so as to face the holding members 8 through 13 of the firstplate member 2 and which are recessed so as to engage the hook portions21 of the holding members 8 through 13. Each of the outside engagingportions 20 has a substantially rectangular planar shape as shown inFIG. 5, and is formed as a recessed portion having a rectangularsectional shape as shown in FIG. 6. The outside engaging portions 20 areformed by recessing a part of the external surface 7 of the second platemember 3, to form a part of the external surface 7. The second platemember 3 has the inside engaging portions 25 so as to correspond to theinside holding members 26 and 27 of the first plate member 2. The insideengaging portions 25 of the second plate member 3 are formed on bothsides (on the right and left sides in FIG. 5) of the hole 31, whichpasses through the second plate member 3 in thickness directions, on theside of the external surface 7. The hole 31 has a rectangular shape soas to be capable of receiving therein the inside holding members 26 and27 (see FIG. 5). Each of the inside engaging members 25 is asubstantially rectangular recess on which the hook portions 30 of theinside holding members 26 and 27 are hooked. Each of the inside engagingmembers 25 has a rectangular planar shape as shown in FIG. 5, and is arecess having a rectangular sectional shape as shown in FIG. 6.

At least one of the first and second plate members 2 and 3 is formed byinjection molding. The surface of the cavity of an injection molding dieis transferred to at least one of the bonded surfaces 2 a and 3 a of thefirst and second plate members 2 and 3 formed by injection molding, sothat fine irregularities are formed thereon. As a result, even if thesecond plate member 3 is pressed on the first plate member 2, anadhesive can permeate fine gaps, which are formed between the bondedsurface 2 a of the first plate member 2 and the bonded surface 3 a ofthe second plate member 3, due to capillarity. Moreover, if it isintended to more precisely form a gap between the bonded surface 2 a ofthe first plate member 2 and the bonded surface 3 a of the second platemember 3 to allow an adhesive 40 to more surely permeate the gap betweenthe bonded surfaces 2 a and 3 a of the members 2 and 3 due tocapillarity, a plurality of fine protrusions 38 are preferably formed onat least one of the bonded surface 2 a of the first plate member 2 andthe bonded surface 3 a of the second plate member 3 as shown in FIGS. 7through 9.

According to the above described constructions, if the second platemember 3 is housed in the space surrounded by the side walls 6 a through6 d of the first plate member 2, the four side faces 14 through 17 ofthe second plate member 3 are guided by the protrusions 35 and 36 of thefirst plate member 2, and the second plate member 3 is mounted on thefirst plate member 2 at a predetermined position. Then, the hookportions 21 of the holding members 8 through 13 of the first platemember 2 engage the outside engaging portions 20 of the second platemember 3, and the hook portions 30 of the inside holding members 26 and27 of the first plate member 2 engage the inside engaging portions 25 ofthe second plate member 3. Thus, the second plate member 3 is held bythe first plate member 2.

Then, an adhesive is dripped from at least one of the four through holes37 of the second plate member 3. At this time, the adhesive is drippedon the first plate member 2 so as not to flow into the first and secondfine grooves 4 and 5. The adhesive permeates a fine gap between thebonded surfaces 2 a and 3 a of the first and second plate members 2 and3, which face each other, due to capillarity, so that the first andsecond plate members 2 and 3 are surely bonded and fixed to each other.The bottom ends of the through holes 37 of the second plate member 3bonded and fixed to the first plate member 2 are communicated with theend portions of the first and second fine grooves 4 and 5 to definestorage portions 37 a which are spaces capable of carrying out storage,injection and extraction of a sample or the like. Furthermore, theadhesive flowing due to capillarity does not enter the first and secondfine grooves 4 and 5 in which the gap between the first and second platemembers 2 and 3 abruptly increases. Therefore, the flow passagesectional area of the first and second fine grooves 4 and 5 can besubstantially constant in longitudinal directions thereof. In additionto the through holes 37, adhesive injecting through holes (not shown)may be formed in the vicinity of the first and second fine grooves 4 and5 in the second plate member 3 at regular intervals along the first andsecond fine grooves 4 and 5 for dripping an adhesive.

According to this preferred embodiment with the above describedconstruction, the second plate member 3 is protected by the side walls 6a through 6 d of the first plate member 2 to prevent external force fromdirectly acting on the edges of the second plate member 3, and it isdifficult for external force shearing the first and second plate members2 and 3 in X and Y directions to act on the bonded surfaces 2 a and 3 aof the first and second plate members 2 and 3. Therefore, even if thesample handling unit 1 drops on the floor during handling or collideswith another obstacle, the adhesive layer sealing the portionssurrounding the first and second fine grooves 4 and 5 is not partiallybroken by cracks or the like, and the function of the fine grooves 4 and5 as microchannels do not deteriorate. In addition, it is difficult forthe bonded surfaces 2 a and 3 a of the first and second plate members 2and 3 to be broken due to peeling.

According to this preferred embodiment, the protrusions 35 formed on theside walls 6 a through 6 d of the first plate member 2, and theprotrusions 36 formed on the holding members 8 through 13 can positionthe second plate member 3 with respect to the first plate member 2 in Xand Y directions, and can prevent the second plate member 3 from beingdisplaced with respect to the first plate member 2 in X and Ydirections. As a result, according to this preferred embodiment, thefirst and second plate members 2 and 3 can be precisely bonded to eachother without the need of any assembling tools. In particular, when thefirst and second plate members 2 and 3 are bonded and fixed to eachother while fine recessed portions (not shown) and so forth formed inthe bonded surface 2 a of the first plate member 2 are aligned with finerecessed portions (not shown) and so forth formed in the bonded surface3 a of the second plate member 3, it is possible to precisely and surelycarry out assembly operation.

According to this preferred embodiment, the second plate member 3 ispressed on the first plate member 2 by the hook portions 21 of theholding members 8 through 13. Therefore, when the first and second platemembers 2 and 3 are bonded and fixed to each other, the bondingoperation of the first plate member 2 to the second plate member 3 canbe easily and surely carried out without the need of any tools forclamping the first and second plate members 2 and 3.

According to this preferred embodiment, the second plate member 3 ispressed on the first plate member 2 by the hook portions 21 of theholding members 8 through 13 to be positioned and fixed with respect tothe first plate member 2 in Z directions. Therefore, even if force in adirection (Z direction) for peeling the second plate member 3 off fromthe first plate member 2 is applied thereon, the holding members 8through 13 can oppose the force. Therefore, there is not the possibilitythat the second plate member 3 is peeled off from the first plate member2 to be damaged.

According to this preferred embodiment, the side faces 14 through 17 ofthe second plate member 3 facing each other are clamped by utilizing theelasticity of the support portions 18 of the holding members 8 through13. Therefore, the second plate member 3 can be held without rattlingthe first plate member 2, so that the bonding operation of the secondplate member 3 to the first plate member 2 can be more precisely andsurely carried out. In addition, according to this preferred embodimentwith such a construction, the side faces 14 through 17 of the secondplate member 3 are elastically held by the holding members 8 through 13of the first plate member 2. Therefore, even if shocks are given to theside walls 6 a through 6 d of the first plate member 2, the shocks aretransmitted to the second plate member 3 while being relaxed by theelasticity of the holding members 8 through 13. As a result, it isdifficult for impact force to act on the bonded surfaces 2 a and 3 a ofthe first and second plate members 2 and 3, so that it is possible toeffectively prevent the sample handling unit 1 from being broken by thepeeling of the bonded surfaces 2 a and 3 a of the first and second platemembers 2 and 3 off from each other.

According to this preferred embodiment, the second plate member 3 can bepressed on the first plate member 2 by the inside holding members 26 and27 formed in the vicinity of the first fine groove 4. Therefore, it ispossible to prevent the central portion (the portion in the vicinity ofthe first fine groove 4) of the second plate member 3 from beingdeformed so as to rise. Thus, the gap between the bonded surfaces 2 aand 3 a of the first and second plate members 2 and 3 can besubstantially constant in the whole area, so that the bonding operationof the first plate member 2 to the second plate member 3 can be moresurely carried out. In particular, according to this preferredembodiment with such a construction, when an adhesive is allowed topermeate the fine gap between the bonded surfaces 2 a and 3 a of thefirst and second plate members 2 and 3 due to capillarity, the adhesivecan uniformly and surely flow in the whole area of the bonded surfaces 2a and 3 a.

According to this preferred embodiment, the side edges of the secondplate member 3 can not only be held by the holding members 8 through 13,but the portions of the second plate member 3 in the vicinity of thefirst fine groove 4 can also be held by the inside holding members 26and 27. Therefore, it is possible to more effectively oppose the forcefor peeling the second plate member 3 off from the first plate member 2.

In the sample handling unit 1 in this preferred embodiment, the sidewalls 6 a through 6 d of the first plate member 2 are formed so as toprotrude upwardly from the external surface 7 of the second plate member3. Therefore, the side walls 6 a through 6 d can surely protect thesecond plate member 3 from impact force and/or external force acting onthe second plate member 3 from the side faces 14 through 17 thereof.

In the above described preferred embodiment, in order to prevent theassembly of the first and second plate members 2 and 3 from beingerroneously carried out, a marker portion 41 is formed by obliquelycutting one of the four corners of the second plate member 3, and afillet portion 42 engageable with the marker portion 41 is formed insideof the cross portion of the side wall 6 a and side wall 6 d of the firstplate member 2.

While the sample handling unit 1 used as a capillary electrophoresischip for carrying out a test in the field of biochemistry has beendescribed as examples for convenience of explanation in the abovedescribed preferred embodiment, the present invention should not belimited thereto, but the sample handling unit 1 in the preferredembodiment may be widely applied to chemical tests in various fieldsother than the field of biochemistry, such as the fields of syntheticchemistry and analytical chemistry.

While the first and second fine grooves 4 and 5 have been formed in thefirst plate member 2 as an example in the above described preferredembodiment, the present invention should not be limited thereto, but thegrooves may be formed in the bonded surface 3 a of the second platemember 3, or in both of the bonded surfaces 2 a and 3 a of the first andsecond plate members 2 and 3.

While the side walls 6 a through 6 d of the first plate member 2 havebeen formed so as to protrude upwardly from the external surface 7 ofthe second plate member 3 in the sample handling unit 1 in the abovedescribed preferred embodiment, the present invention should not belimited thereto, but the side walls 6 a through 6 b may be formed so asnot to protrude from the external surface 7 of the second plate member3.

While the first and second plate members 2 and 3 have been bonded toeach other with an adhesive in the sample handling unit 1 in the abovedescribed preferred embodiment, means for bonding the first and secondplate members 2 and 3 to each other according to the present inventionshould not be limited to that in the above described preferredembodiment, but bonding means, such as laser welding, ultrasonic weldingor heat welding, may be applied.

While the first and second plate members 2 and 3 have been formed of asynthetic resin as an example in the above described preferredembodiment, the present invention should not be limited thereto, butthey may be formed of a glass or metal material. If the first and secondplate members 2 and 3 are formed of a glass or metal material, means forbonding the members 2 and 3 to each other may be means suitable forbonding of the glass or metal material, in addition to the bonding meansdescribed as an example in the above described preferred embodiment.

While the adhesive has been allowed to permeate the gap between thebonded surface 2 a of the first plate member 2 and the bonded surface 3a of the second plate member 3 due to capillarity after the mounting ofthe second plate member 3 on the first plate member 2 in the abovedescribed preferred embodiment, the present invention should not belimited thereto, but an adhesive may be previously applied on at leastone of the bonded surface 2 a of the first plate member 2 and the bondedsurface 3 a of the second plate member 3 before the second plate member3 is mounted on the first plate member 2.

While the sectional shape of the first and second fine grooves 4 and 5has been square in the above described preferred embodiment, the presentinvention should not be limited thereto, but the sectional shape may beanother shape, such as semicircle, U-shape or substantially triangle.

According to the present invention, the number and position of theprotrusions 35 and 36 should not be limited to those in the abovedescribed preferred embodiment shown in FIG. 1. The number and positionsof the protrusions 35 and 36 may be suitably changed as long as thesecond plate member 3 can be positioned with respect to the first platemember 2 while it is possible to prevent the second plate member 3 frombeing displaced with respect to the first plate member 2. For example,only the protrusions 36 of the holding members 8 through 13 may beformed to omit the protrusions 35. Alternatively, only the protrusions35 may be formed on the side walls 6 a through 6 d to omit theprotrusions 36 of the holding members 8 through 13.

The bottom faces 24 of the hook portions 21 of the holding members 8through 13, and the outside engaging portions 20 contacting the bottomfaces 24, have been formed on a plane substantially in parallel to thebonded surface 2 a in the above described preferred embodiment (see FIG.2), the bottom faces 24 of the hook portions 21 of the holding members 8through 13 and the outside engaging portions 20 may be inclined withrespect to the bonded surface 2 a to allow the bottom faces 24 of thehook portions 21 to depress the outside engaging portions 20 (inclinedface) of the second plate member 3 obliquely downwards as shown in FIG.10. With such a construction, the side faces 14 through 17 of the secondplate member 3 facing each other can be clamped by the holding members 8through 13, and the second plate member 3 can be pressed on the firstplate member 2 by the holding members 8 through 13. As a result, it ispossible to effectively prevent the second plate member 3 from beingdisplaced with respect to the first plate member 2 by the holdingmembers 8 through 13, so that it is possible to prevent the bondedsurface 2 a of the first plate member 2 from being peeled off from thebonded surface 3 a of the second plate member 3.

The side walls 6 a through 6 d of the first plate member 2 have beenformed so as to substantially surround the whole area of the four sidefaces 14 through 17 of the second plate member 3 other than the holdingmembers 8 through 13 in the above described preferred embodiment, thepresent invention should not be limited thereto, but the side walls 6 athrough 6 d may be partially formed so as to protect the four corners ofthe second plate members 3 as shown in FIG. 11. Also with thisconstruction, it is possible to prevent impact force from actingdirectly on the second plate member 3 when the dropping or the like ofthe sample handing unit 1 occurs, and it is difficult for external forceto act on the bonded surfaces 2 a and 3 a of the first and second platemembers 2 and 3, so that it is difficult for the bonded surfaces 2 a and3 a of the first and second plate members 2 and 3 to be peeled off fromeach other.

In the above described preferred embodiment, the holding members 8through 13 and the inside holding members 26 and 27 may be omitted, andthe side walls 6 a through 6 d of the first plate member 2 may becontinuously formed so that each of the side walls 6 a through 6 d hasthree protrusions 35 for positioning both end portions and substantiallycentral portion in longitudinal directions of each of the side faces 14through 17 of the second plate member 3 as shown in FIG. 12.

In the above described preferred embodiment, the holding members 8through 13, the inside holding members 26 and 27, and the side walls 6 athrough 6 d may be omitted, and the first plate member 2 may be largerthan the second plate member 3 so as to protrude from the side faces 14through 17 of the second plate member 3 as shown in FIGS. 13A and 13B.With such a construction, during fall or the like, the larger firstplate member 2 is easy to collide with the floor or the like prior tothe smaller plate member 3, and it is difficult for the first and secondplate members 2 and 3 to simultaneously collide with the floor or thelike, so that it is difficult for great force to act on the bondedsurfaces 2 a and 3 a of the first and second plate members 2 and 3 topeel them off from each other.

In the above described preferred embodiment, the side walls 6 a through6 d may be omitted, and the second plate member 3 may be positioned andfixed on the first plate member 2 by the holding members 8 through 13and inside holding members 26 and 27 as shown in FIG. 14. In theembodiment shown in FIG. 14, the holding members 8 through 13 may beomitted, and the second plate member 3 may be positioned and fixed onthe first plate member 2 by only the inside holding members 26 and 27.Alternatively, as shown in FIG. 15, the second plate member 3 may bepositioned and fixed on the first plate member 2 by the holding members8 through 13. Furthermore, in the case of the embodiment shown in FIG.14, the second plate member 3 is positioned with respect to the firstplate member 2 in X and Y directions by means of the protrusions 36 ofthe holding members 8 through 13, and the second plate member 3 ispositioned and fixed on the first plate member 2 in Z directions bymeans of the hook portions 21 of the holding members 8 through 13 andthe hook portions 30 of the inside holding members 26 and 27. In thecase of the embodiment shown in FIG. 15, the second plate member 3 ispositioned with respect to the first plate member 2 in X and Ydirections by means of the protrusions 36 of the holding members 8through 13, and the second plate member 3 is positioned and fixed on thefirst plate member 2 in Z directions by means of the hook portions 21 ofthe holding members 8 through 13.

While the planar cross-shaped fine groove has been formed by the firstand second fine grooves 4 and 5 in the first plate member 2 in the abovedescribed preferred embodiment, a fine groove having cross, Y-shape,curve or another complicated shape may be formed in the first platemember 2.

While the sample handling unit 1 has been formed by bonding the firstthin plate member 2 and the second thin plate member 3 to each other inthe above described preferred embodiment, the present invention shouldnot be limited thereto, but a sample handling unit may be formed bybonding block pieces (first and second members) having any one ofvarious shapes, not thin plate, to each other. Also in this case,recessed portions, such as fine grooves, for allowing the movement ofthe like of a sample are formed in the bonded surface of at least one ofthe block pieces.

In the above described preferred embodiment, one of the first platemember (first member) 2 and the second plate member (second member) 3may be divided into a plurality of parts which are bonded to the othermember.

While the fine grooves (the first fine groove 4 and the second finegroove 5) have been formed in the surface of one member (e.g., the firstplate member 2) which is covered with another member (the second platemember 3) to form the sample handling unit 1 having a fine passagetherein so as to allow a sample to move in the passage in the abovedescribed preferred embodiment, the present invention should not belimited thereto, but the invention may be applied to a sample handlingunit which is formed by bonding at least two members and in which asample can be moved, stored or held. For example, in addition to thesample handing unit wherein a sample is movable in the first and secondfine grooves 4 and 5, the present invention can be applied to a samplehandling unit wherein a plurality of wells capable of storing therein asample are formed in the surface of one (substrate) of first and secondmembers so as to be set in array and wherein a protective member (theother of the first and second members) is bonded to the surface of thesubstrate to cover the opening portions of the wells to protect thesample in the wells. In addition, according to the present invention,both of a microchannel (first recessed portion) for moving a sample, anda microwell (second recessed portion) for housing therein the sample maybe formed in the bonded portion of the first plate member (first member)to the second plate member (second member).

According to the present invention, as shown in FIG. 16, if a pair ofprotrusions 50 butting against the wall of the hole 31 are formed on theside faces of the support portions 28 of the inside holding members 26and 27 and if the protrusions 50 are pressed on the wall of the hole 31while the support portions 28 are elastically deformed, force in anopposite direction to the X direction in the figure acts on the wall ofthe hole 31 by the pair of protrusions 50. As a result, the insideholding members 26 and 27 protrude in the hole 31, and the second platemember 3 is held on the first plate member 2 by frictional forceproduced in the contact portion of the protrusions 50 of the insideholding members 26 and 27 with the wall face of the hole 31. Accordingto such a modified example, the first and second plate members 2 and 3can be integrated with each other by greater force in cooperation withthe advantageous effects in the above described preferred embodiment.

While the hook portions 21 of the holding members 8 through 13 haveengaged the outside engaging portions 20 of the second plate member 3 inthe above described preferred embodiment, the present invention shouldnot be limited thereto, but the hook portions 21 of the holding members8 through 13 may be hooked directly on the external surface 7 of thesecond plate member 3 without forming the outside engaging portions 20on the second plate member 3. Thus, it is not required to recess a partof the external surface 7 of the second plate member 3 to form theoutside engaging portions 20.

According to the present invention, for example, in FIG. 1, the secondplate member 3 may be pressed on the side wall 6 b of the first platemember 2 by the holding member 13, and the second plate member 3 may beclamped by the holding member 13 and side wall 6 b to be held on thefirst plate member 2. Even if the second plate member 3 is thus held bythe holding members 8 through 13 and the side walls 6 a through 6 d ofthe first plate member 2 facing the holding members 8 through 13, it ispossible to effectively prevent the bonded surfaces of the first andsecond plate members 2 and 3 from being peeled off from each other.

As described above, according to the present invention, in a samplehandling unit formed by bonding first and second members to each other,it is difficult for external force to act in a direction in which thefirst and second members are peeled off from each other. Therefore, itis possible to effectively prevent the sample handling unit from beingbroken by the peeling of the bonded surfaces of the first and secondmembers off from each other, and it is possible to effectively preventdesired functions from deteriorating in accordance with the partialbreakage of the bonded surfaces of the first and second members.

Referring to the accompanying drawings, particularly to FIGS. 17Athrough 25, the preferred embodiments of a microfluidic device accordingto the present invention will be described below in detail.

First Preferred Embodiment

FIGS. 17A and 17B show the first preferred embodiment of a microfluidicdevice 101 according to the present invention. FIG. 17A is a plan viewof the microfluidic device 101, and FIG. 17B is a partially sectionalside of the microfluidic device 101 view taken along line XVIIB-XVIIB ofFIG. 17A.

As shown in FIGS. 17A and 17B, three kinds of microchips 106, 107 and108 having fine grooves (recessed portions) 103, 104 and 105 havingdifferent shapes are arranged on the top face of a plate-like basemember 102 so as to be set in array. That is, as shown in FIG. 17A, in asubstantially left half region on the base member 102, ten microchips106 of the first kind are arranged in two columns (first and secondcolumns). In a substantially right half region on the base member 102,five microchips 107 of the second kind are arranged in the third column,and five microchips 108 of the third kind are arranged in the fourthcolumn which the rightmost column on the base member 102. The basemember 102 is associated with the microchips 106 through 108 of thefirst through third kinds arranged on the base member 102 for formingthe microfluidic device 101.

In this preferred embodiment, the base member 102 and the microchips 106through 108 of the first through third kinds are formed byinjection-molding a resin material, such as polycarbonate (PC) orpolymethylmethacrylate (PMMA). Furthermore, the material of the basemember 102 and microchips 106 through 108 of the first through thirdkinds should not be limited to the above described resin materials, butthey may be formed of a polymeric material, such as polydimethylsiloxane(PDMS), an ultraviolet curable resin, an inorganic material, such as aglass material, or a metal material.

As shown in FIG. 18A, the microchip 106 of the first kind has asubstantially rectangular planar shape. In one surface 106 a of themicrochip 106, there is formed a cross-shaped fine groove 103 comprisinga fine groove 103 a linearly extending in lateral directions of themicrochip 106, and a fine groove 103 b linearly extending in directionsperpendicular to the fine groove 103 a. In both end portions of each ofthe fine grooves 103 a and 103 b, through holes 110 through 113 areformed.

As shown in FIG. 18B, the microchip 107 of the second kind has asubstantially rectangular planar shape. In one surface 107 a of themicrochip 107, there is formed a fine groove 104 comprising a finegroove 104 a linearly extending in lateral directions of the microchip107, a fine groove 104 b linearly extending in directions perpendicularto the fine groove 104 a, and fine grooves 104 c through 104 f which arefirst through fourth sub-grooves sequentially communicated with the finegroove 104 b downstream of the fine groove 104 a (on the right side ofthe fine groove 104 a in the figure). In both end portions of each ofthe fine grooves 104 a and 104 b and in the opposite end portions of thefine grooves 104 c through 104 f to the end portions communicated withthe fine groove 104 b, through holes 114 through 122 are formed.Furthermore, the microchip 107 of the second kind has the same size asthat of the microchip 106 of the first kind.

As shown in FIG. 18C, the microchip 108 of the third kind has asubstantially rectangular planar shape. In one surface 108 a of themicrochip 108, there is formed a fine groove 105 comprising a finegroove 105 a linearly extending in lateral directions of the microchip108, and a fine groove 105 b perpendicular to the fine groove 105 a. Thefine groove 105 b has a meander portion 105 c meandering downstream ofthe fine groove 105 b (on the right side of the fine groove 105 a) forensuring a sufficient length for mixing, reaction, analysis or the like.In both end portions of each of the fine grooves 105 a and 105 b,through holes 123 through 126 are formed. Furthermore, the microchip 108of the third kind has the same size as that of the microchip 106 of thefirst kind.

Each of the fine grooves 103 a, 103 b, 104 a through 104 f, 105 a and105 b forming the fine grooves 103, 104 and 105 in this preferredembodiment has a width and depth of 50 micrometers, but the width anddepth should not be limited thereto. The width and depth of the finegroove may be suitably set in the range of from 1 to 10000 micrometersin accordance with the kind of a specimen moving in a passage, which isformed by closing the opening portion of each of the fine grooves 103 a,103 b, 104 a through 104 f, 105 a and 105 b as described later, and thekind of a fluid in the passage, or in accordance with the driving forceor the like of the specimen or fluid.

As shown in FIGS. 17A through 18C, after the surface (surface 106 a, 107a or 108 a) of each of the microchips 106 through 108 having the finegroove 103, 104 or 105 is arranged so as to face the base member 102, apair of positioning holes 127 formed in the corner portions indirections of a diagonal line of each of the microchips 106 through 108are engaged with a pair of positioning pins 128 formed so as to protrudefrom the base member 102, and each of the microchips 106 through 108 isbonded to the base member 102, so that the opening of each of the finegrooves 103 through 105 is closed by the surface 102 a of the basemember 102. Thus, passages 132 through 134 are formed, and one endportion of each of the through holes 110 through 126 is closed to formreservoirs (storage portions) 110A through 126A. Furthermore, thepositioning holes 127 of the microchips 106 through 108 are associatedwith the positioning pins 128 of the base member 102 for forming apositioning means for mounting the microchips 106 through 108 on thebase member 102 while positioning the microchips 106 through 108 withrespect to the base member 102. The microchips 106 through 108 may beintegrated with the base member 102 by a fixing method (e.g., ultrasonicwelding) other than adhesion.

For example, in the microchip 106 of the first kind of the microchips106 through 108 with such a construction, an electrophoretic solution isinjected into the passage 132 from any one of the reservoirs 110Athrough 113A, and a sample is injected from any one of the reservoirs112A and 113A in the end portions of the shorter passage 132 a.Thereafter, a high voltage is applied between both end portions of thepassage 132 a crossing the longer passage 132 b. Thus, the samplemigrates in the passage 132 a toward the cross portion in which thepassage 132 a crosses the passage 132 b. Then, when the sample migratesto the cross portion in which the passage 132 a crosses the passage 132b, a migration voltage is applied between both end portions of thelonger passage 132 b. Thus, a very small amount of sample in the crossportion, in which the passages 132 a and 132 b cross, migrates in theanalyzing passage 132 c. Therefore, a detector (not shown), such as afluorophotometer or an ultraviolet-visible light spectrophotometer, ispreviously arranged at an appropriate position in the analyzing passage132 c so as to be capable of analyzing the sample migrating in theanalyzing passage 132 c.

It is considered that means for forming a patterned electrode (notshown) on the bonded surface of the microchips 106 to the base member102 to allow a current to pass through the electrode to simultaneouslyapply a voltage to a column of microchips 106 is used as means forapplying a voltage between both end portions of each of the passages 132a and 132 b. Alternatively, means for suitably inserting an electrodeinto each of the reservoirs 110A through 113A to apply a voltage may beused. In the microchip 107 of the second kind, a sample in the passage133 can migrate by applying a voltage to any one of the reservoirs 114Athrough 122A. In the microchip 108 of the third kind, a sample in thepassage 134 can migrate by applying a voltage to any one of thereservoirs 123A through 126A.

In the microfluidic device 101 with the above described construction,after the base member 102 and various microchips 106 through 108 areseparately formed, microchips 106 through 108 of kinds necessary forintended purpose, such as analysis, can be selected to be suitablycombined to be positioned and fixed on the base member 102. Therefore,according to this preferred embodiment, when the microchips 106 through108 are formed by injection molding, the size of an injection moldingdie can be decreased, and the die can be easily worked, so that the costof producing the die can be decreased. Since the shape of the basemember 102 is also simple, the cost of producing the base member 102 canbe decreased. As a result, the microfluidic device 101 in this preferredembodiment can be more inexpensively produced than a conventional devicewherein a large number of microchannels are formed in a single plate soas to be set in array. In addition, according to this preferredembodiment, the components of the microfluidic device 101 can beminiaturized, so that it is possible to reduce the rate of occurrence ofdefective units to improve production efficiency to reduce the price ofproducts.

In the microfluidic device 101 in this preferred embodiment, variousmicrochips 106 through 108 having fine grooves 103 through 105 havingdifferent shapes can be suitably combined in accordance with intendedpurpose, such as analysis, so that it is possible to simply carry outanalysis or the like for general purpose.

In FIG. 17A, the upper-left corner portion 130 of the base member 102 ischamfered, and the upper-left corner portion 131 of each of themicrochips 106 through 108 is chamfered. Thus, it is possible to preventeach of the microchips 106 through 108 from being mounted on the basemember 102 in an erroneous attitude.

While the sample has migrated by electrophoresis in the passages 132through 134 of the microchips 106 through 108 in this preferredembodiment, the present invention should not be limited thereto. Asample may be moved by utilizing capillarity, or a portion for moving asample due to capillarity may be combined with a portion for moving asample by electrophoresis. Alternatively, a sample may be moved byutilizing a pressure difference, such as positive or negative pressure,as driving force.

While the microchips 106 through 108 of the first through third kindshave been used as an example in the preferred embodiment, plural kindsof microchips having fine grooves (microchannels) having a shape otherthan that of the fine grooves 103 through 105, and/or plural kinds ofmicrochips having a large number of wells (fine recessed portions) maybe combined to be formed on the base member 102.

While the positioning holes 127 have been formed in the microchips 106through 108 and the positioning protrusions 128 have been formed on thebase member 102 in the preferred embodiment, the present inventionshould not be limited thereto. Positioning protrusions may be formed onthe microchips 106 through 108, and positioning holes engageable withthe positioning protrusions may be formed in the base member 102.

The fine grooves 103 through 105 of the microchips 106 through 108 maybe previously closed by a film or the like to be arranged on the basemember 102 without closing the fine grooves 103 through 105 by the basemember 102.

In the preferred embodiment, storage portions (not shown) serving assample storages having an increased flow passage sectional area may besuitably formed in the middle of each of the passages 132, 133 and 134.

Second Preferred Embodiment

FIGS. 19A through 21 show the second preferred embodiment of amicrofluidic device 141 according to the present invention. FIG. 19A isa plan view of the microfluidic device 141 in this preferred embodiment,and FIG. 19B is a partially sectional side view of the microfluidicdevice 141 taken along line XIXB-XIXB of FIG. 19A. FIG. 20 is anenlarged view of a part of FIG. 19A, and FIG. 21 is an enlargedsectional view of a part of FIG. 19A.

As shown in these figures, twenty microchip housing recesses 143 fordetachably housing therein microchips 106 through 108 are formed in thetop face of a plate-like base member 142 so as to be arranged in theform of an array of four columns×five rows. The microchips 106 of thefirst kind are housed in the microchip housing recesses 143 of twocolumns (the first and second columns), and the microchips 107 of thesecond kind are housed in the microchip housing recesses 143 of thethird column. The microchips 108 of the third kind are housed in themicrochip housing recesses 143 of the fourth column. Thus, the basemember 142 is associated with the microchips 106 through 108 of thefirst through third kinds for forming the microfluidic device 141.

In this second preferred embodiment, if the microchips 106 through 108are housed in the microchip housing recesses 143, the microchips 106through 108 are positioned with respect to the base member 142 bypositioning protrusions 146 which are formed on side walls 144 a, 144 b,145 a and 145 b of each of the microchip housing recesses 143.Therefore, the microchips 106 through 108 are not formed with thepositioning holes 127 in the first preferred embodiment, and the basemember 142 is not formed with the positioning pins 128 in the firstpreferred embodiment (see FIGS. 19A, 19B and 20). In the secondpreferred embodiment, the microchips 106 through 108 may be formed ofthe same material as that in the first preferred embodiment using thesame working method as that in the first preferred embodiment. On theother hand, the base member 142 is precisely formed by injectionmolding. Furthermore, in this preferred embodiment, the positioningprotrusions 146 of the microchip housing recesses 143 function as meansfor positioning the microchips 106 through 108 on the base member 142.

The planar size of each of the microchip housing recesses 143 is largerthan that of each of the microchips 106 through 108. Each of themicrochip housing recesses 143 has chip pressing claws 147 on the sidesof both end portions of each of a pair of longer facing edge portions(side walls 144 a and 144 b) thereof, and in the substantially centralportions of each of a pair of shorter facing edge portions (side walls145 a and 145 b) thereof. In addition, each of the microchip housingrecesses 143 has positioning protrusions 146, which are engageable withthe side faces of the microchips 106 through 108 via a slight gap, inthe substantially central portion of each of the pair of longer facingedge portions (the side walls 144 a and 144 b) in longitudinaldirections, and on the sides of both end portions of each of the pair ofshorter facing edge portions (the side walls 145 a and 145 b) inlongitudinal directions.

As shown in FIG. 21, each of the chip pressing claws 147 comprises anupright wall 147 a which is elastically deformable independently ofother portions of the base member 142, and a protruding portion 147 bwhich protrudes from a side face of the upper portion of the uprightwall 147 a toward a corresponding one of the microchip housing recesses143. The upper portion of the protruding portion 147 b is formed with achamfered portion 147 c which is obliquely cut in the vicinity of thetip of the protruding portion 147 b. If the upper portion of theprotruding portion 147 b is thus formed with the chamfered portion 147c, the edge portion 152 of the bottom face of each of the microchips 106through 108 can press a corresponding one of the chip pressing claws 147to expand a corresponding one of the microchip housing recesses 143, sothat a corresponding one of the microchips 106 through 108 can be easilyinserted into the corresponding one of the microchip housing recesses143. On the sides of the back face and both side faces of each of thechip pressing claws 147, a deeper groove 148 than the depth of acorresponding one of the microchip housing recesses 143 is formed so asto surround the corresponding one of the chip pressing claws 147 (seeFIG. 20). With such a construction, each of the chip pressing claws 147is easy to be flexibly deformed toward its back face which is oppositeto the corresponding one of the microchip housing recesses 143, so thatthe operation for attaching and detaching each of the microchips 106through 108 to and from the corresponding one of the microchip housingrecesses 143.

In a portion of each of the microchips 106 through 108 facing thecorresponding one of the chip pressing claws 147, an engaging recess 150engageable with the protruding portion 147 b of the corresponding one ofthe chip pressing claws 147 is formed so as to be cut out.

As shown in FIG. 21, a portion which is arranged in each of themicrochip housing recesses 143 and which is positioned directly belowthe protruding portion 147 b of the corresponding one of the chippressing claws 147, is communicated with the bottom face of the basemember 142 via a hole 151. Thus, the base member 142 can be formed byinjection molding regardless of the presence of the under-cut portion (aportion in which the protruding portion 147 b is formed) of each of thechip pressing claws 147.

With such a construction, when each of the microchips 106 through 108 isintended to be mounted in a corresponding one of the microchip housingrecesses 143, the edge portion 152 of the bottom face of a correspondingone of the microchips 106 through 108 first contacts the chamferedportion 147 c of a corresponding one of the chip pressing claws 147, sothat the corresponding one of the microchips 106 through 108 enters thecorresponding one of the microchip housing recesses 143 while thecorresponding one of the microchips 106 through 108 presses and flexiblydeforms the corresponding one of the chip pressing claws 147. Then, whenthe corresponding one of the microchips 106 through 108 reaches thebottom face 153 of the corresponding one of the microchip housingrecesses 143, the corresponding one of the chip pressing claws 147elastically restores to its original attitude, so that the protrudingportion 147 b of the corresponding one of the chip pressing claws 147engages the engaging recess 150 of the corresponding one of themicrochips 106 through 108. Thus, it is possible to prevent thecorresponding one of the microchips 106 through 108 from disengagingfrom the corresponding one of the microchip housing recesses 143, sothat the corresponding one of the microchips 106 through 108 can be heldon the base member 142.

On the other hand, when the microchips 106 through 108 are intended tobe detached from the microchip housing recesses 143, all of the chippressing claws 147 are simultaneously pressed to be open by an exclusivechip detaching tool (not shown) and the microchips 106 through 108 aregrasped. Then, while all of the chip pressing claws 147 are pressed tobe open by the chip detaching tool, the microchips 106 through 108 aretaken out. Thus, the microchips 106 through 108 can be detached from thebase member 142.

In such a microfluidic device 141 in this preferred embodiment, afterthe base member 142 and the microchips 106 through 108 of plural kindsare separately formed, the microchips 106 through 108 of kinds necessaryfor the base member 142 are selected, and the microchips 106 through 108of the selected kinds can be suitably combined to be mounted in themicrochip housing recesses 143 of the base member 142. Therefore,according to this preferred embodiment, if the microchips 106 through108 are formed by injection molding, the injection molding die can beminiaturized and can be easily worked, so that the cost of producing thedie can be reduced. In addition, since the base member 142 can be easilyformed by injection molding, working costs can be reduced. As a result,the microfluidic device 141 in this preferred embodiment can be moreinexpensively produced than a conventional device wherein a large numberof microchannels are formed in a single plate so as to be set in array.

In the microfluidic device 141 in this preferred embodiment, themicrochips 106 through 108 can be detachably mounted in the microchiphousing recesses 143. Therefore, various microchips 106 through 108having fine grooves 103 through 105 having different shapes can besuitably combined in accordance with intended purpose, such as analysis,so that it is possible to simply carry out analysis for general purpose.

Furthermore, in FIG. 20, a fillet portion 154 is formed in theupper-left corner portion of each of the microchip housing recesses 143of the base member 142, and a chambered portion 155 engageable with thefillet portion 154 of a corresponding one of the microchip housingrecesses 143 is formed in the upper-left corner portion of each of themicrochips 106 through 108. Thus, it is possible to prevent each of themicrochips 106 through 108 from being mounted on the base member 142 inan erroneous attitude.

In this preferred embodiment, the microchips 106 through 108 are held onthe base member 142 by means of the chip pressing claws 47. Therefore,even if the microfluidic device 141 drops onto the floor or the like toreceive shocks, it is possible to prevent the microchips 106 through 108from being detached from the base member 142 to fly over the floor orthe like. At this point, in the case of a microfluidic device wheremicrochips are only bonded and fixed to a base member, if themicrofluidic device drops onto the floor or the like, the microchips arepeeled off from the base member by shocks, so that there is thepossibility that the microchips are detached from the base member to flyover the floor or the like.

While the engaging recesses 150 formed in the microchips 106 through 108have been designed to engage the chip pressing claws 147 formed on thebase member 142 so that the microchips 106 through 108 are held on thebase member 142 in this preferred embodiment, the external surfaces ofthe microchips 106 through 108 may be directly pressed and held by thechip pressing claws 147.

In this preferred embodiment, the protruding portions 147 b of the chippressing claws 147 are preferably pressed on the microchips 106 through108 by utilizing elastic force caused by the flexible deformation of thechip pressing claws 147, so that the microchips 106 through 108 aresurely held on the base member 142 by the elastic force of the chippressing claws 147. Thus, it is possible to prevent the microchips 106through 108 from being dislocated in the microchip housing recesses 143by force acting on the contact surfaces of the chip pressing claws 147to the engaging recesses 150.

In this preferred embodiment, the fine grooves 103 through 105 of themicrochips 106 through 108 shown in FIG. 18A though 18C previouslyclosed by another member (e.g., a thin plate member or film) other thanthe base member 142 may be detachably attached on the base member 142without closing the fine grooves 103 through 105 by the base member 142.

Third Preferred Embodiment

FIG. 22 shows the third preferred embodiment of a microfluidic device161 according to the present invention. In this preferred embodiment,one reservoir 111A (115A, 124A) of adjacent two of microchips 106through 108 is communicated with the other reservoir 112A (116A, 125A)of the adjacent two of the microchips 106 through 108 via acommunication passage 163 formed in a base member 162.

With such a construction, after a first analysis is carried out by thefirst microchip 106 (107, 108), a sample used in the first analysis canbe fed to the second microchip 106 (107, 108) via the communicationpassage 163 in the base member 162 to be subsequently mixed with anothersample or reagent to carry out a second analysis. Thus, the sample canbe continuously analyzed by the microchips 106 (107, 108) connected toeach other by the communication passage 163 in the base member 162.

While a column of microchips 106 (107, 108) (extending in verticaldirections in FIG. 22) have been connected to each other by means of thecommunication passages 163 in this preferred embodiment, the presentinvention should not be limited thereto. For example, a row ofmicrochips 106 through 108 of the first through third kinds (extendingin lateral directions in FIG. 22) may be connected to each other bymeans of communication passages (not shown) formed in the base member162. That is, the reservoirs 111A and 110A of adjacent two of microchips106 of the first kind in lateral directions may be communicated witheach other via a communication passage, the reservoir 111A of themicrochip 106 of the first kind and the reservoir 114A of a microchip107 of the second kind adjacent thereto in lateral directions beingcommunicated with each other via a communication passage, and thereservoir 115A of the microchip 107 of the second kind and the reservoir123A of a microchip 108 of the third kind adjacent thereto in lateraldirections being communicated with each other via a communicationpassage, so that a sample may be continuously analyzed by means of themicrochips 106 through 108.

Alternatively, sample receiving holes (not shown) may be recessed to beformed in portions of the base member 162 corresponding to thereservoirs 110A through 124A (see FIGS. 17A and 17B) of the microchips106 through 108, the sample receiving hole of one of the microchipsbeing connected to the sample receiving hole of the other microchip bymeans of a tube (passage) (not shown) embedded in the base member 162,so that a sample used in the one of the microchips may be continuouslyused in the other microchip.

Fourth Preferred Embodiment

FIG. 23 shows a microfluidic device 171 wherein a plurality ofmicrochips 106 through 108 are connected to each other by connectingmeans K so as to be set in array. In this preferred embodiment, each ofthe microchips 106 through 108 has a first arm 173, which is formed onone of a pair of facing longer side faces and which has a protrusion 172at the tip thereof, and a second arm 175 which is formed on the otherside face of the pair of facing longer side faces and which has a recess174 in the tip end. Each of the microchips 106 through 108 also has athird arm 177, which is formed on one of a pair of facing shorter sidefaces and which has a protrusion 176 at the tip thereof, and a fourtharm 180 which is formed on the other side face of the pair of facingshorter side faces and which has a recess 178 in the tip end thereof.The microchips 106 through 108 adjacent to each other in verticaldirections in FIG. 23 are connected to each other by the engagement ofthe protrusion 172 of the first arm 173 with the recess 174 of thesecond arm 175. The microchips 106 through 108 adjacent to each other inlateral directions in FIG. 23 are connected to each other by theengagement of the protrusion 176 of the third arm 177 with the recess178 of the fourth arm 180. That is, the first arm 173, second arm 175,third arm 177 and fourth arm 180 are associated with each other forforming the connecting means K.

In this preferred embodiment, a base member (not shown) for closingthrough holes 110 through 126 and fine grooves 103 through 105 on theside of the reverse is secured to the reverse of each of the microchips106 through 108 so as to correspond to each of the microchips 106through 108, so that reservoirs 110A through 126A and communicationpassages 132 through 134 are formed. The base member (not shown) may beformed of the same hard material as that of the microchips 106 through108, or of a soft material, such as a film material.

With such a construction, an optional number of plural kinds ofmicrochips 106 through 108 for different intended purposes or the like(e.g., the shape of microchannels and wells) can be freely combined.

Fifth Preferred Embodiment

FIG. 24 shows a microfluidic device 181 as a modified example of thefourth preferred embodiment shown in FIG. 23. In this preferredembodiment, a pair of positioning holes 127 are formed in the cornerportions in directions of a diagonal line of each of the microchips 106through 108, and a pair of positioning protrusions 128 engageable withthe positioning holes 127 of a corresponding one of the microchips 106through 108 are formed in a base member 102. Furthermore, in thispreferred embodiment, holes (not shown) for receiving the positioningprotrusions 28 are formed in the same base member as that in the fourthpreferred embodiment. In this preferred embodiment, even if themicrochips 106 through 108 are only supported on the base member 102, asample in each of passages 132 through 134 of the microchips 106 through108 does not leak out.

According to this preferred embodiment with such a construction, whenthe carriage or the like of the microfluidic device 181 having themicrochips 106 through 108, which are connected to each other by theconnecting means K to be set in array, is carried out, the connectingstate of the microchips 106 through 108 is maintained by the base member102, so that the carriage or the like of the microfluidic device 181 canbe easily carried out. In addition, when a specific portion of the basemember 102 is used as a reference point for continuously carrying outanalysis, the position of analysis in each of the microchips 106 through108 can be precisely determined, so that it is possible to decrease thedispersion in the results of analysis, which is caused by the dispersionin position of analysis.

Furthermore, when the base member 102 is caused to function as only acarrying tray, it is not required to position the microchips 106 through108 on the base member 102. Therefore, it is not required to form thepositioning holes 127 in the microchips 106 through 108, and it is notrequired to form the positioning protrusions 128 on the base member 102.

Sixth Preferred Embodiment

FIG. 25 is an exploded perspective view of the sixth preferredembodiment of a microfluidic device 191 according to the presentinvention. As shown in FIG. 25, a first microchip 193 having a finegroove (recessed portion) 192 is stacked on a base member 194 so thatthe surface of the first microchip 193 having the fine groove 192 facesthe base member 194. In addition, a second microchip 196 having a finegroove (recessed portion) 195 is staked on the first microchip 193 sothat the surface of the second microchip 196 having the fine groove 195faces the first microchip 193 and so that a through hole 197 of thesecond microchip 196 is communicated with a through hole 198 of thefirst microchip 193. Thus, the base member 193, and first and secondmicrochips 193 and 196 are associated with each other for forming themicrofluidic device 191. Furthermore, the bonded surfaces of the firstand second microchips 193 and 196 are connected or welded to each otherto close the bottom end portion of the through hole 198 by the basemember 194 to form a reservoir 200 and to close the openings of the finegrooves 192 and 195 by the base member 194 to form passages 201 and 202.

With such a construction, after a sample moves in the passage 202 of thesecond microchip 196 due to capillarity in a direction of arrow R1 tomove in the reservoir 200 of the second microchip 196 and firstmicrochip 192 in a direction of arrow R2, the sample moves in thepassage 201 of the first microchip 193 due to capillarity in a directionof arrow R3.

If the plurality of microchips 193 and 196 are thus combinedthree-dimensionally (stacked in vertical directions), many analyses canbe efficiently carried out in a narrow area. If such a construction iscombined with the first preferred embodiment, it is possible tosimultaneously carry out a larger number of analyses of samples, and itis possible to provide an inexpensive microfluidic device 191.

While the two microchips 193 and 196 have been stacked in this preferredembodiment, the present invention should not be limited thereto, but alarger number of microchips may be stacked.

As described above, in the microfluidic device according to the presentinvention, after the base member and various microchips are separatelyformed, microchips of kinds necessary for intended purpose, such asanalysis of a sample, can be selected to be suitably combined to bepositioned on the base member. Therefore, according to the presentinvention, when microchips are molded, a molding die can be miniaturizedand easily worked, so that it is possible to decrease the cost ofproducing the die. Since the base member of a microfluidic deviceaccording to the present invention has a simple shape, it is possible todecrease the cost of producing the base member. As a result, themicrofluidic device according to the present invention can be moreinexpensively produced than a conventional device wherein a large numberof microchannels are formed in a single plate so as to be set in array.

In the microfluidic device according to the present invention, variousmicrochips having different structures of recessed portions can besuitably combined in accordance with intended purpose, such as analysis.Therefore, it is possible to easily carry out general purpose (e.g.,mixing and analysis of a sample).

In the microfluidic device according to the present invention, themicrochips are detachably held by the chip pressing claws formed on thebase member. Therefore, even if the device drops onto the floor or thelike to receive shocks, the microchips are not detached from the basemember.

The microfluidic device according to the present invention can beutilized for various purposes by suitably combining various microchips.That is, the microfluidic device according to the present invention canbe utilized as a chemical device for carrying out separation, analysis,mixing, reaction, concentration or the like of samples, e.g., fineorganisms, such as viruses or bacterium, vital formations, such as cellsor biopolymers, organic compounds other than biopolymers, inorganics,and inorganic compounds.

While the present invention has been disclosed in terms of the preferredembodiment in order to facilitate better understanding thereof, itshould be appreciated that the invention can be embodied in various wayswithout departing from the principle of the invention. Therefore, theinvention should be understood to include all possible embodiments andmodification to the shown embodiments which can be embodied withoutdeparting from the principle of the invention as set forth in theappended claims.

1. A microfluidic device comprising: a base member; a plurality ofmicrochips, each of which has a space defined therein for transporting asample, said plurality of microchips being mounted on said base memberso as to be set in array; and a chip pressing claw, wherein saidplurality of microchips are detachably held by said chip pressing clawof said base member.
 2. A microfluidic device as set forth in claim 1,wherein each of said plurality of microchips has a recessed portionwhich is closed by said base member to define said space.
 3. Amicrofluidic device as set forth in claim 1, wherein said space is apassage for allowing said sample to move therein.
 4. A microfluidicdevice as set forth in claim 3, wherein said passage has a storageportion for storing therein said sample.
 5. A microfluidic device as setforth in claim 4, wherein said storage portion of one of said pluralityof microchips is communicated with said storage portion of another ofsaid plurality of microchips via a communication passage formed in saidbase member.
 6. A microfluidic device as set forth in claim 1, whereinone of adjacent two of said plurality of microchips has an engagingprotrusion which protrudes toward the other of the adjacent two of saidplurality of microchips, and the other of the adjacent two of saidplurality of microchips has an engaged recess which is engaged with saidengaging protrusion of the one of adjacent two of said plurality ofmicrochips.
 7. A microfluidic device as set forth in claim 1, whereinsaid plurality of microchips are positioned with respect to said basemember by positioning means.